Hi SteveZ
I'm new to this forum, so hello all!
An excellent place to discuss gag cartooning would be the Cartoonist Club's forum
CCGB FORUM
Techniques are different for every cartoonist, and it depends upon your style. if you want to maintain your spontaneous line in a gag cartoon, then there's nothing wrong with going straight in with the pen. Equally, you can pencil first, but I think it's important not to slavishly follow your pencil line or you'll suck the energy out of the gag. I speak from experience - I'm still trying to loosen up my style and have found using a brush pen helps. Still not entirely happy with my work ....
As Lew said, the joke's the thing - as long as it's funny, that's what counts.
Weekly news are probably the worst payers in the gag market. It was about a tenner a gag a few years ago and I don't think it's got any better, so personally I wouldn't bother with them. At the other end of the market, Readers Digest and Private Eye are good payers and treat the cartoonists well. (repeat fees, selling originals etc)
If you're going into gag cartooning as a hobby, then you'll enjoy it, but it's incredibly hard to make a full time career out of it. The markets have shrunk to practically nothing as opposed to the multitude of mags and papers that took them 35 years ago. (You should have started sending them then! - I couldn't, I was only 4

) Most gag cartoonists have several other markets they work in - illustration, cards, etc
Anyway, all the best with your cartooning
Any questions, email me